The project involves the determination of the crystal structures of metal chelates which are of relevance to the treatment of metal poisoning. The metals being studied include those which are of known high toxicity and with which people come into routine contact. The chelating agents involved in the project are cysteine and its derivatives (including Penicillamine), BAL, and derivatives of EDTA, which are currently used in the treatment of individuals who have been subjected to metal poisoning. The purpose of these structural studies is to determine which ligand sites are involved in the binding of the chelates to specific metals, and to see which bonds are in need of strengthening. This information will enable us to propose chemical modification of the ligands for application in the treatment of exposure to individual metals, and eventually should produce one or more effective antidotes for each of the metals under study.